JMS

Asynchronous communication in Java

Michał Szynkiewicz

Examples: https://github.com/michalszynkiewicz/jms-examples

Email: michal.l.szynkiewicz@gmail.com

What's the point?Why do we need asynchronicity?

@POST public Response addCustomer(CustomerDto customer) {

validateCustomer(customer); storeCustomer(customer); return status(CREATED).build();

}

@POST public Response addCustomer(CustomerDto customer) { validateCustomer(customer); storeCustomer(customer); sendConfirmationLink(customer.getEmail()); return status(CREATED).build(); }

Solution: send email asynchronously

+ A standard+ Multiple implementations+ Loose coupling-/+ intermediary server- one way communication- Java API

What's JMS

● Queue

● Topic

Communication schemes

Queue

Usage in our case

Usage in our case

Usage in our case

● Queue

● Topic

Communication schemes

Topic

When to use topic?

Topic use case: Error logging

Topic use case: Error logging

Topic use case: Error logging

Topic use case: Error logging

●Headers: ● e.g. JMSCorrelationID, JMSPriority

●Properties● application-specific headers

●Body● e.g. a String, Map, Object

Message

● Choosing a subset of all messages● SQL-like syntax● Can only use properties and headers

E.g. “JMSPriority = 6 and myProperty='someValue'”

Message selectors

Message selectors

Reliability

Message acknowledgement

● Message are kept on server until message acknowledgment comes ●Acknowledgement modes:

● AUTO — automatic● CLIENT — manual (message.acknowledge())● DUPS_OK — batch, may result in duplicates

● Messages that failed to be processed, can be redelivered● Can be immediate or delayed● After maximum number of redeliveries message ends up in DLQ

Message redelivery

Message persistence

● When JMS server goes down — messages are still kept ● May be disabled

Common issue: Request-response

On specJMS test it was able to handle 8M per second.

It uses disk storage for persistence.

Source: http://planet.jboss.org/post/8_2_million_messages_second_with_specjms

How fast can it be?On example of HornetQ

Available at github: https://github.com/michalszynkiewicz/jms-examples

Spring code examples

Not much :)

● Simplified API● Asynchronous sending (your code doesn't have to wait for JMS provider)● Delivery delay

What's new in JMS 2.0

●AMQP+ cross-platform, full-feature, widely used- protocol still evolving, not backward compatible. Only few providers implement current version.

●STOMP+ via HTTP, widely implemented, lightweight- protocol doesn't describe destination types, etc

●MQTT+ extremely lightweight, used on mobile devices- no queue (topic only), no message properties (only

headers)

(Some) other messaging standards

Questions?

Дякую

email:michal.l.szynkiewicz@gmail.com